The present invention relates generally to integrated circuit devices, and, more particularly, to a method and apparatus for monitoring integrated circuit temperature through path delays.
In an integrated circuit device, the various functions performed by the logic elements on a chip are dependent on variations in the chip operating conditions, such as temperature. Ideally, the operating temperature for processing of a digital signal by a device, such as a gate, is constant and within the parameter range(s) assumed in the digital design. As a practical matter, the operating temperature associated with signal processing by a given device can vary with time, depending upon the present circumstances and recent history of operation of the device. Moreover, chips are often contained in enclosures that may experience extreme variations in temperature. Consequently, if the device temperature varies too much from the assumed idealized value, undesirable device responses such as poor chip performance or even device malfunction can occur.
On the other hand, when a chip fails to perform properly or crashes, any one or more of a variety of factors could actually be the cause. In order to determine the exact cause of a chip failure, complex recording devices may be used to store information on the operating state of the chip before the failure. These recording devices can store specific information such as the chip temperature, chip operating voltages and other process variables. However, these devices typically require the use of complex analog sensors or fast analog-to-digital (A/D) converters that can detect and report the status of these variables on a real time basis. Such recording devices may also store the chip states in various registers located on the chip at predetermined intervals.
One drawback associated with these types of recording devices is the large amount of space that they consume on the chip, as well as the increased amount of processing needed to continually update the status of all the variables. Still another drawback is that analog sensors are often sensitive to noise caused by digital switching operations and other factors. Additionally, the cost of such recording devices with a number of analog sensors increases with the complexity of the particular device.
Accordingly, it would be desirable to be able to determine which specific locations within an IC that may exhibit temperature fluctuations due to process variation over the IC or the function in which the circuitry in that location is performing. Furthermore, having cross IC temperature information is useful for controlling intra-chip voltage levels, and to provide a designer with temperature information during module testing. This information is preferably obtained in a manner that uses existing device features, to the extent possible.